1. Field of the Invention
The present invention relates to ovens for heat treating manufactured parts, and in particular to ovens which are equipped with conveying means moving the parts through the oven chamber.
2. Description of the Prior Art
Various heat treatment ovens with conveying means are known. One such prior art oven is a so-called shaking hearth oven, having a shaking trough reaching through the oven chamber, the parts to be treated being loaded on one end of the trough and conveyed through the oven through the shaking action of the trough. This shaking conveyance is obtained through pulsing thrusts applied to the trough by means of a pneumatic cylinder. The shaking trough extends through the entire length of the oven, which may have one or two heating zones and which may be heated with gas or electrically.
Among the shortcomings of this prior art device are that the shaking trough and the parts to be treated must be protected against direct heat radiation in each oven zone by means of a muffle; that difficulties exist therefore in connection with the circulation of the oven atmosphere, so that the gas components necessary for the surface treatment of the parts come in contact with all parts surfaces and that the heat is distributed evenly; and that due to the pulsing thrusts applied to the shaking trough and the resulting impact stress, in combination with uneven heat distribution, buckling occurs on the shaking trough surface, with the result of impeded parts conveyance.
It has also been found that small parts, especially miniature parts and special parts, when treated in a shaking hearth installation, lead to damaging heat stress on the trough, because of their high bulk weight, resulting likewise in an impairment of the evenness of conveyance and of the quality of heat treatment.